Method for detecting engine rotation direction

Abstract

A method for determining a direction of rotation of a rotatable shaft includes rotating a disk in synchronization with the rotatable shaft. The disk has a plurality of contiguous zones, and the zones include a set of first zones and at least one second zone. Each of the first zones has first and second areas. The method also includes generating a sensor signal using a sensor disposed adjacent the disk in response to the passing of the zones as the disk rotates. The sensor signal generated during the passing of the first zone is different than the sensor signal generated during the passing of the at least one second zone. The method further includes determining periods between the passing of the first areas of the first zones based on the sensor signal, detecting the at least one second zone based on the sensor signal, and determining the direction of rotation based on the periods determined after the detection of the at least one second zone.

1 . A method for determining a direction of rotation of a rotatable shaft, comprising:
 rotating a disk in synchronization with the rotatable shaft, the disk having a plurality of contiguous zones, the zones including a set of first zones and at least one second zone, each of the first zones having first and second areas;   generating a sensor signal using a sensor disposed adjacent the disk in response to the passing of the zones as the disk rotates, the sensor signal generated during the passing of the first zone being different than the sensor signal generated during the passing of the at least one second zone;   determining periods between the passing of the first areas of the first zones based on the sensor signal;   detecting the at least one second zone based on the sensor signal; and   determining the direction of rotation based on the periods determined after the detection of the at least one second zone.   
   
   
       2 . The method of  claim 1 , further including determining a change in period following the detection of the at least one second zone, the direction of rotation being determined based on the determined change in periods. 
   
   
       3 . The method of  claim 1 , further including detecting a local maximum period after the detection of the at least one second zone, the direction of rotation being determined based on the detected local maximum period. 
   
   
       4 . The method of  claim 3 , wherein the determining of the direction of rotation includes:
 determining a difference in time between the detection of the local maximum period and the detection of the at least one second zone, and   determining the direction of rotation based on the determined time difference.   
   
   
       5 . The method of  claim 4 , wherein the determination of the time difference includes determining a number of the periods between the detection of the local maximum period and the detection of the at least one second zone. 
   
   
       6 . The method of  claim 1 , wherein the second zone and the second area of the first zone terminate at a first radial distance from a center of the disk, and the first area of the first zone terminates at a second radial distance from the center of the disk. 
   
   
       7 . The method of  claim 6 , wherein the first area of the first zone is a tooth, the second area of the first zone is a notch, and the second zone is a notch. 
   
   
       8 . The method of  claim 1 , wherein the first and second zones are of approximately equal angular extent. 
   
   
       9 . The method of  claim 1 , wherein the period is measured by at least one of time and crank angle. 
   
   
       10 . A system for determining a direction of rotation of a rotatable shaft, comprising:
 a disk rotatable in synchronization with the rotatable shaft having a plurality of contiguous zones, the zones including a set of first zones and at least one second zone, each of the first zones having first and second areas;   a sensor disposed adjacent the disk for generating a sensor signal in response to the passing of the zones as the disk rotates, the sensor signal generated during the passing of the first zone being different than the sensor signal generated during the passing of the at least one second zone; and   a controller coupled to the sensor, the controller being configured to:
 receive the sensor signal from the sensor, 
 determine periods between the passing of the first areas of the first zones based on the sensor signal, 
 detect the at least one second zone based on the sensor signal, and 
 determine the direction of rotation based on the periods determined after the detection of the at least one second zone. 
   
   
   
       11 . The system of  claim 10 , wherein the controller is further configured to:
 determine the change in period following the detection of the at least one second zone, and   determine the direction of rotation based on the determined change in periods.   
   
   
       12 . The system of  claim 10 , wherein the controller is further configured to:
 detect a local maximum period after the detection of the at least one second zone, and   determine the direction of rotation based on the detected local maximum period.   
   
   
       13 . The system of  claim 12 , wherein the controller is further configured to:
 determine a number of periods between the detection of the local maximum period and the detection of the at least one second zone, and   determine the direction of rotation based on the determined number of periods.   
   
   
       14 . A method for determining a direction of rotation of an engine, comprising:
 rotating a disk in synchronization with a shaft of the engine, the disk having a plurality of contiguous zones of approximately equal angular extent, the zones including a set of first zones and at least one second zone, each of the first zones having first and second areas, the first zones being different than the at least one second zone;   generating a sensor signal using a sensor disposed adjacent the disk in response to the passing of the zones as the disk rotates;   determining periods between the passing of the first areas of the first zones based on the sensor signal; and   determining the direction of rotation based on the determined periods.   
   
   
       15 . The method of  claim 14 , further including:
 detecting the at least one second zone based on the sensor signal; and   determining the direction of rotation based on the periods determined after the detection of the at least one second zone.   
   
   
       16 . The method of  claim 14 , further including determining a change in period, the direction of rotation being determined based on the determined change in periods. 
   
   
       17 . The method of  claim 16 , detecting a local maximum period, the direction of rotation being determined based on the detected local maximum period. 
   
   
       18 . The method of  claim 17 , wherein the determining of the direction of rotation includes:
 determining a difference in time between the detection of the local maximum period and the detection of the at least one second zone, and   determining the direction of rotation based on the determined time difference.   
   
   
       19 . The method of  claim 14 , wherein the determined direction of rotation is a reverse direction of rotation, and the method further includes preventing fuel injectors of the engine from firing after determining that the direction of rotation is the reverse direction. 
   
   
       20 . The method of  claim 14 , wherein the determined direction of rotation is a reverse direction of rotation, and the method further includes altering a firing order of fuel injectors of the engine after determining that the direction of rotation is the reverse direction.